Antennas are critical components in communications, radar and direction finding systems, interfacing between the RF circuitry and the environment. RF circuitry is often manufactured using printed circuit board (PCB) technology, and numerous engineering and commercial advantages are realized by integrating the RF antennas directly on the same printed circuit boards as the circuitry. Doing so improves product quality, reliability, and form-factor compactness, while at the same time lowering manufacturing costs by eliminating fabrication steps, connectors, and mechanical supports.
There is a variety of PCB antennas, including microstrip patch antennas that radiate perpendicularly to the PCB, slot antennas that radiate perpendicularly to the PCB in both directions, and printed Vivaldi and Yagi antennas that radiate parallel to the surface of the PCB. Cavity-backed antennas were implemented in PCB technology as well, especially at the higher frequencies. These antennas have dimensions on the order of the half-wavelength of the operating frequency, and at lower frequencies consume considerable PCB area.
Because of close proximity to the ground plane, however, PCB RF antennas typically have a narrow-band response, which is disadvantageous when wideband performance is needed, such as for ultra-wideband (UWB) operation in the 3.1-10.6 GHz band, or even a 6-8.5 GHz sub-band. Additional applications of interest are millimeter wave bands of the 57-71 GHz (“60 GHz”) ISM band, 71-76 GHz and 81-86 GHz communications bands, and the 76-81 GHz automotive radar band. Covering these bands, or combinations thereof calls for antennas with large fractional bandwidth.
Thus, it would be desirable to have PCB antennas with enhanced bandwidth and improved wide-band matching characteristics. This goal is met by embodiments of the present invention.